public int heightmapMaximumLOD { get; set; }

Use on low-end graphics cards to block the highest level of detail for Terrain. A value of 0 for this property allows the terrain to be shown at the highest detail. A value of 1 reduces the maximum triangle count to one-fourth of its current value and halves the width and height of the heightmap resolution.

using UnityEngine;public class Example : MonoBehaviour{    void Start()    {        Terrain.activeTerrain.heightmapMaximumLOD = 1;    }}